PROJECT SUMMARY Introduction of combined anti-retroviral therapy (cART) in the mid 90th has significantly decreased the rate of mortality and enhanced the quality of life of HIV-infected individuals. However as the HIV+ population ages, cardiovascular diseases (CVD) and neurologic complications are increased, which reflects the complex pathophysiological interactions in this population. Identification of early biomarkers that could identify subjects at higher risks for these complications would help better manage aging HIV-infected patients. We have recently identified the over-expression of proinflammatory isoforms of the novel cytokine IL-32 as a robust biomarker that can predict control failure in HIV-infected subjects with a history of slow disease progression. IL-32 is an inflammatory cytokine that induces multiple other inflammatory cytokines such as IL-6, IL-1? and TNF?; all of which are involved in CVD. IL-32 over-expression in vascular tissues is directly associated with CVD. The mechanism(s) behind the over-expression of IL-32 in HIV infection, particularly in treated subjects, remain elusive. IL-32 is part of the innate immune response to viral and bacterial infections and therefore, heightened expression is likely mediated by residual HIV replication under cART but also by other microbial agents that might egress from a dysbiosed gut, weakened in the event of Th17 cell depletion. In this proposal, we aim to demonstrate that over-expression of the proinflammatory isoforms of IL-32 results in cardiac complications that increase with aging. As we showed that IL-32 could robustly predict disease progression in HIV infection several years in advance, we expect to establish the same predictability for cardiac complications. In Specific aim 1, we will take advantage of two large cohorts (The Canadian Cohort of HIV and Aging (CCHA) directed by Dr Cecile Tremblay and the WIHS cohort, directed by our co-applicant Dr Robert Kaplan) to generate a map of expression for the different isoforms of IL-32 in young versus old HIV-infected men and women. We will correlate these measures with a panel of well-established inflammatory biomarkers and subclinical clinical CVD markers such as calcium score, IMT as well as with CVD clinical outcomes. In Specific Aim 2, we will study the interplay between IL-32 expression and HIV reservoirs and residual viremia by comparing young and old groups of HIV infected individuals from the same cohorts. We also aim to study the ability of HIV residual replication to up-regulate IL-32 pro-inflammatory isoforms expression and to down-regulate the less inflammatory ones. In Specific aim 3, we will investigate the impact of intestinal dysbiosis on the induction of IL-32 proinflammatory isoforms by intestinal epithelium. We will also determine the impact of IL-32 production on Th17/Treg ratio at the mucosal and systemic levels in correlation with HIV-related CVD. Together, the overarching goal of this project is to demonstrate that IL-32 is a central player in systemic inflammation and a mediator of CVD and that this cytokine can be used as a predictive biomarker for disease but also as a therapeutic target to modulate inflammatory processes and tackle HIV reservoirs.